// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.

#include "gtest/gtest.h"
#include "leveldb/filter_policy.h"
#include "util/coding.h"
#include "util/logging.h"
#include "util/testutil.h"

namespace leveldb {

    static const int kVerbose = 1;

    static Slice Key(int i, char *buffer) {
        EncodeFixed32(buffer, i);
        return Slice(buffer, sizeof(uint32_t));
    }

    class BloomTest : public testing::Test {
    public:
        BloomTest() : policy_(NewBloomFilterPolicy(10)) {}

        ~BloomTest() { delete policy_; }

        void Reset() {
            keys_.clear();
            filter_.clear();
        }

        void Add(const Slice &s) { keys_.push_back(s.ToString()); }

        void Build() {
            std::vector<Slice> key_slices;
            for (size_t i = 0; i < keys_.size(); i++) {
                key_slices.push_back(Slice(keys_[i]));
            }
            filter_.clear();
            policy_->CreateFilter(&key_slices[0], static_cast<int>(key_slices.size()),
                                  &filter_);
            keys_.clear();
            if (kVerbose >= 2) DumpFilter();
        }

        size_t FilterSize() const { return filter_.size(); }

        void DumpFilter() {
            std::fprintf(stderr, "F(");
            for (size_t i = 0; i + 1 < filter_.size(); i++) {
                const unsigned int c = static_cast<unsigned int>(filter_[i]);
                for (int j = 0; j < 8; j++) {
                    std::fprintf(stderr, "%c", (c & (1 << j)) ? '1' : '.');
                }
            }
            std::fprintf(stderr, ")\n");
        }

        bool Matches(const Slice &s) {
            if (!keys_.empty()) {
                Build();
            }
            return policy_->KeyMayMatch(s, filter_);
        }

        double FalsePositiveRate() {
            char buffer[sizeof(int)];
            int result = 0;
            for (int i = 0; i < 10000; i++) {
                if (Matches(Key(i + 1000000000, buffer))) {
                    result++;
                }
            }
            return result / 10000.0;
        }

    private:
        const FilterPolicy *policy_;
        std::string filter_;
        std::vector<std::string> keys_;
    };

    TEST_F(BloomTest, EmptyFilter
    ) {
    ASSERT_TRUE(!Matches("hello"));
    ASSERT_TRUE(!Matches("world"));
}

TEST_F(BloomTest, Small
) {
Add("hello");
Add("world");
ASSERT_TRUE(Matches("hello")
);
ASSERT_TRUE(Matches("world")
);
ASSERT_TRUE(!Matches("x"));
ASSERT_TRUE(!Matches("foo"));
}

static int NextLength(int length) {
    if (length < 10) {
        length += 1;
    } else if (length < 100) {
        length += 10;
    } else if (length < 1000) {
        length += 100;
    } else {
        length += 1000;
    }
    return length;
}

TEST_F(BloomTest, VaryingLengths
) {
char buffer[sizeof(int)];

// Count number of filters that significantly exceed the false positive rate
int mediocre_filters = 0;
int good_filters = 0;

for (
int length = 1;
length <= 10000;
length = NextLength(length)
) {
Reset();

for (
int i = 0;
i<length;
i++) {
Add(Key(i, buffer)
);
}

Build();

ASSERT_LE(FilterSize(),

static_cast
<size_t>((length
* 10 / 8) + 40))
<<
length;

// All added keys must match
for (
int i = 0;
i<length;
i++) {
ASSERT_TRUE(Matches(Key(i, buffer))
)
<< "Length " << length << "; key " <<
i;
}

// Check false positive rate
double rate = FalsePositiveRate();
if (kVerbose >= 1) {
std::fprintf(stderr,
"False positives: %5.2f%% @ length = %6d ; bytes = %6d\n",
rate * 100.0, length, static_cast

<int> (FilterSize())

);
}
ASSERT_LE(rate,
0.02);  // Must not be over 2%
if (rate > 0.0125)
mediocre_filters++;  // Allowed, but not too often
else
good_filters++;
}
if (kVerbose >= 1) {
std::fprintf(stderr, "Filters: %d good, %d mediocre\n", good_filters,
mediocre_filters);
}
ASSERT_LE(mediocre_filters, good_filters
/ 5);
}

// Different bits-per-byte

}  // namespace leveldb

int main(int argc, char **argv) {
    testing::InitGoogleTest(&argc, argv);
    return RUN_ALL_TESTS();
}
